Method

The first thing you need to do is grind the walnuts, which you can do very carefully using the 'pulse' switch on a food processor (if this is overdone, the nuts go pasty and oily). Otherwise, a hand-held nut grinder will do the job.

To make the shortbread, place the butter and sugar in a large mixing bowl and cream them together until pale and fluffy. Then mix the sifted flour and rice flour together and gradually work this into the creamed mixture, a tablespoonful at a time.

Next, add the ground walnuts and use your hands to form the mixture into a smooth dough. Leave the dough to rest in a plastic food bag in the fridge for 30 minutes, then roll it out on a lightly floured work surface to a round approximately 8 inches (20 cm) in diameter.

Now, using the 1¾ inch (4.5 cm) cutter, cut out approximately 20 rounds, re-rolling the trimmings. Place them on the lightly greased baking sheet and bake in the oven for 45 minutes.

Cool them for 5 minutes before transferring to a wire rack. When completely cool, dust them with icing sugar and store in an airtight container.